In many manufacturing operations, the workpiece has to be kept in the operator's view while it is being manipulated for the intended purpose. Drilling, brazing, heat treatment, soldering and welding processes in various machining and manufacturing industries are some of the processes where the workpiece needs to be viewed from a remote location while work is in progress. Machines designed for these operations, therefore, include optical viewing systems or assemblies located at a position remote from the workpiece or work area.
Welding or drilling processes in general, and electron or laser beam welding or drilling in particular, require that the relative positions of the heat source, (which is the electron beam for electron beam welders and the laser beam for laser beam welders), and the weld joint be accurately established prior to the initiation of the welding cycle. This is especially crucial for electron beam welding because electron beam welding is an electric fusion welding process whereby a stream or beam of electrons is focused and made to impinge on a workpiece to melt it.
Electron beam welding and drilling machines and methods for the use thereof are generally known in the art. Electron beam welding is normally carried out in a high vacuum. The weldments produced are, therefore, relatively narrow. As a result, making visual alignment of the heat source and the weld joint becomes very difficult without an accurate establishment of their relative positions.
The major components of an electron beam welding machine generally comprise a suitable source for electrons such as the electron gun, a vacuum chamber large enough to house the workpiece, means for viewing the weld zone while welding is in progress and means for manipulating and adjusting the relative positions of the workpiece, the electron beam and the work table. To facilitate the requirements for proper alignment, most electron beam welding machines incorporate a monocular viewing device or system which permits the operator to view the welding area and to establish the correct position of the heat source relative to the weldment area. These monocular systems characteristically have restricted field of view, impaired depth perception, and limited welding effectiveness. A few commercially available units have recently included binocular eyepieces but the optical path remains essentially monocular with its attendant restrictions and limitations as mentioned above. Some of these prior art devices are exemplified in the following patents.
U.S. Pat. No. 4,304,982, "Optical Viewing System Associated Apparatus And Machines Equipped Therewith", issued Dec. 8, 1981 to James R. Gramse, describes replaceable shields for the optical components of the viewing system for protecting them from condensation of corrosive vapors which may be generated during the welding process.
U.S. Pat. No. 4,090,056, "Optical Viewing System For An Electron Beam Welder", issued May 16, 1978 issued to Herbert C. Lockwood and Salvatore M. Robelotto, is directed to an arrangement for protecting the optical system from vapor deposition and from the effects of radiation, and electrical charge.
All of these prior art viewing systems for electron beam welding devices use monocular viewing systems and do not address themselves to the problems associated with the narrow, restricted view path and depth of vision while the welding is in progress. These prior art optical viewing systems consist of a horizontally mounted monocular vision tube with internal illumination and reflecting mirrors which provide an optical line of sight along the electron beam. For welding facilities which handle a variety of workpiece sizes, weld configurations, a wide range of materials and dissimilar combinations, these viewing or monitoring systems with their attendant limitations, adversely affect weld quality and hamper productivity. Continuous welding operations carried out over long periods of time using monocular viewing systems, can also result in eye fatigue thereby interfering with the operator's visual accuity. This, in turn, results in diminished welding effectiveness. The prior art monocular viewing systems, therefore, suffer from the above disadvantages.
The foregoing status of the art indicates that there is a need for a viewing system which provides for not only a larger field of view and magnification of the workpiece but also a stereoscopic view thereof. It would, therefore, be desirable to have a viewing system, especially suited for application in electron beam welding, which produces both a magnified view of the weld area and a stereoscopic view, particularly considering the fact that the electron beam typically used is very narrow.